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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2024 · Paper I

Q5(e)(ii). Why Hf is placed below Zr

Question

Hf is placed below Zr in the periodic table. Justify the statement.

Answer in brief

Hf (Z = 72) has the outer configuration 5d²6s², matching the 4d²5s² of Zr, so it belongs to group 4 below Zr; because of the lanthanide contraction the two atoms are almost equal in size and their chemistry is nearly identical.

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Topic notes: lanthanides and actinides (lanthanide contraction, magnetic moments, separation), with every Civil Services, IFoS and Geo-Scientist PYQ →

Covershafniumzirconiumlanthanide contractiongroup 4 elementselectronic configuration

All parts of Question 5